Microphones are commonly used in vehicular applications for a variety of purposes. In some applications the microphone is used for cellular telephones, vehicle navigation, safety, and voice recognition systems. A typical prior art microphone system 100 is depicted in FIG. 1, wherein a microphone transducer 101 feeds a gain or amplifier 103 and provides an amplified audio output 105 for an electronic device. One drawback of typical German Association of the Automotive Industry (VDA) microphone vehicular systems occurs when one microphone is used to drive multiple electronic devices. Prior art FIG. 2 illustrates a microphone transducer system 200 where the microphone 201 is connected to the amplification state 203 and then to multiple electronic devices 205, 207, 209 in the vehicle. Those skilled in the art will recognize that the bias point of the microphone will not remain constant when driving multiple devices. Typically electric microphone systems require that the bias remain at a fixed value (typically ½ the supply voltage) which is approximately 4 Volt direct current (VDC) in a VDA system, while the VDA standard dictates an 8 Volt supply voltage and 820 Ohm pull-up resistance for the vehicular microphone. Therefore, paralleling multiple VDA supplies into the microphone 201, will reduce the load resistance which will alter the amplifier bias point. This will ultimately cause a greater degree of clipping and/or other distortion products in the audio from the microphone 201, which is input into one or more electronic devices attached thereto. Prior VDA microphone systems have had to accept reduced performance when connected to multiple loads/inputs or resort to elaborate switching systems to connect the microphone to only one active electronic device input at a time.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.